Solar power charging device with self-protection function

Abstract

A solar power charging device with a self-protection function is provided, which includes a solar cell, a rechargeable battery, and a diode. The solar cell defines an open-circuit voltage Voc and an operating voltage Vop, in which the Voc is slightly higher than the Vop. The rechargeable battery defines a battery voltage, an operating voltage of load Vload, and a maximum charging voltage Vf, in which the Vf is substantially equal to the Voc. The diode has an anode connected to the solar cell and a cathode connected to the rechargeable battery. When the battery voltage of the rechargeable battery is lower than the Vop, the solar cell provides the rechargeable battery a fully-efficient charging current. When the battery voltage is raised to be equal to the Voc, the solar cell provides the rechargeable battery a charging current of zero, thus preventing the rechargeable battery from being overcharged.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a solar power charging device with a self-protection function, in particular to a charging device capable of preventing overcharge employing physical properties of a solar cell and a rechargeable battery by selecting a suitable open-circuit voltage of the solar cell and maximum charging voltage of the rechargeable battery.[0003]2. Related Art[0004]Since rechargeable batteries capable of being charged and reused repeatedly have been designed in the industry, the consumption of primary batteries and environment pollution caused thereby have been effectively reduced. However, when the electric energy of the rechargeable battery is not enough, it must be taken down for charging, which causes inconvenience in use. Furthermore, due to shortage of energy sources, the solar energy, as a convenient and free energy source without pollution, has become a main trend for the new energy sources.[0005]...

AI Technical Summary

Benefits of technology

[0007]Accordingly, the present invention is directed to a solar charger with a self-protection function, which utilizes the matching effect between an open-circuit voltage of a solar cell and a voltage of a rechargeable battery to avoid overcharge without adding an overcharge protection device additionally, such that the rechargeable battery supplies voltage continuously or is charged continuously, and the safety and service life of the rechargeable battery are not affected.

[0009]When the battery voltage of the rechargeable battery is lower than the operating voltage of the solar cell, the solar cell provides the rechargeable battery a fully-efficient charging current (a maximal charging current that can be provided by the solar cell under the same intensity of illumination), such that the electric energy of the rechargeable battery consumed by the load device can be compensated by the solar cell rapidly, and thus the rechargeable battery can keep powering the load device continuously. When the battery voltage of the rechargeable battery is raised to be equal to the open-circuit voltage of the solar cell, the solar cell provides the rechargeable battery a charging current of zero. Therefore, the voltage of the rechargeable battery never exceeds its maximum charging voltage, and thus ensuring the safety of the rechargeable battery.

[0011]Since the common solar photovoltaic products are mostly designed to have the rechargeable batteries being fully charged, in order to avoid the overcharge circumstance, a schottky diode is installed at a terminal of the solar cell merely when the solar output current is lower than 300 mA and the rechargeable battery is a low-volume and low-density battery, such as a lead acid battery, so as to prevent the current within the rechargeable battery from reversely flowing back to the solar cell, and to be directly connected to a rechargeable battery for use. However, with the structure of the present invention, even when the solar output current is higher than 300 mA or the rechargeable battery is a high-volume and high-density battery, such as a lithium battery, a self-protection effect for the solar charger can be achieved by selecting a suitable solar cell and a rechargeable battery.

Problems solved by technology

However, when the electric energy of the rechargeable battery is not enough, it must be taken down for charging, which causes inconvenience in use.

As a result, the open-circuit voltage of the solar cell is higher than the operating voltage of the solar cell by about 30%, so that it is worried that the rechargeable battery may be overcharged.

The structure mentioned above must employ an overcharge protection and control device to protect the battery, as a result, not only the members are complex and the cost cannot be reduced, but also there is a risk of component failure.

Therefore, currently, how to reduce the elements (overcharge and over-discharge controller) to realize a simple and reliable solar charger is an urgent issue in the solar charger field.

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